Original article
Comparison of body mass index
of a national cohort of Maltese children
over a 3-year interval
Victoria Farrugia Sant’Angelo, Victor Grech
Abstract
Introduction
Aims: To compare body mass index (BMI) at 7 years and at
9 years of age in a national cohort of children in Malta, born in
2001, and to compare the results with an earlier study carried
out in 2007 in this same cohort. Methods: BMI measurement
of all children in the second year of formal school and again in
the fourth year.
Results: In 2008, data was collected from a total of 3435
children (girls 48.9%, boys 51.1%) with a mean age of 6.8 years.
The same procedure was carried out in 2010 on the same cohort
of children. A total of 3090 children participated in the second
round of data collection (girls 49.5%, boys 50.5%). Based on
WHO criteria (using the 2007 WHO Child Growth Reference
BMI-for-age 5-19 charts), over a quarter of Maltese children
aged 7 years were found to be overweight or obese in 2008.
This proportion rose to just over 40% when the same cohort was
measured in 2010 at the age of 9 years. A significant prevalence
of overweight and obese boys was found in Gozo for both studies.
Children attending Independent (fee-paying) schools were the
least overweight and obese.
Discussion: Obesity in childhood in Malta is increasing
despite efforts to curb this disease. More emphasis must
be made on prevention strategy in childhood as this is a key
factor in reducing the burden of morbidity and mortality of
childhood disease.
Overweight and obesity constitute a global health problem
and contribute significantly to the onset of non-communicable
diseases such as diabetes, hypertension, stroke, ischaemic heart
disease and malignancies. Obese children tend to become obese
adults and for this reason, body mass index (BMI) is routinely
measured as part of the health surveillance performed by the
school doctor and nurse in Malta’s primary schools. This study
follows a cohort of Maltese children born in 2001 who initially
had height and weight taken routinely for BMI purposes in
2007,1 and who were similarly re-measured in 2008 and 2010.
Keywords
Overweight, children, epidemiology, body mass index, obese,
obesity/burden of disease
Victoria Farrugia Sant’Angelo* MA, MMCFD
Primary Child Health and Immunisation Unit,
Primary Health Directorate
Email: victoria.farrugia-santangelo@gov.mt
Victor Grech PhD, FRCPCH
Department of Paediatrics, Mater Dei Hospital, Msida Malta
Methods
Equipment and data collection
The methodology used was the same as that utilised in
an earlier study carried out on Maltese children in 2007.1 All
measurements were performed using portable stadiometers
(SECA 214 Portable Stadiometer) and portable digital scales
(BEURER PS07 Digital Weighing Scales) by school medical
doctors and nurses. Height was measured following the standard
method for stadiometer usage, with the head in the Frankfurt
plane. Children’s height and weight were taken according to
previously established protocol in that children were measured
dressed in light clothing. This consisted of a shirt/blouse,
trousers/skirt, underwear and socks. Measurements were taken
in the school clinic and the confidentiality of each student was
maintained. Both data sets were collected over a seven-week
period, between the first week of April and third week of May in
2008 and 2010 respectively. All measurements were taken by 8
registered nurses specialised and experienced in school nursing.
These nurses work on a regional basis and have pre-assigned
schools that they are responsible for. The Independent schools
were distributed accordingly.
The data was inputted by two data-input clerks into a MS
Excel spreadsheet. Both completed data sets were merged and
cleaned by one of the authors (VFS). Children who were absent
from school on the day of the examination were eliminated from
the study, as were children who were repeating the scholastic
year. Summary statistics, t-tests (assuming unequal variance)
and one-factor analysis of variance (ANOVA) were used to
compare means.
The overall results were compared with the previous (2007)
study as this same cohort (born in 2001) had also been studied
*corresponding author
34
Malta Medical Journal Volume 23 Issue 01 2011
Table 1: Regional subdivision of districts in Malta
N. Harbour
S. Harbour
West
North
S. East
Qormi
Vittoriosa
Rabat
Mellie˙a
B’Bugia
B’Kara
Cospicua
Dingli
M©arr
M’Scala
GΩira
Floriana
Attard
Mosta
G˙axaq
Óamrun
Kalkara
Ba˙rija
St Paul’s Bay
Gudja
Msida
Senglea
Mdina
G˙arg˙ur
Kirkop
Pembroke
Valletta
Ûebbu©
Naxxar
M’Xlokk
Ba˙ar iç-Çag˙aq
Mqabba
Pietà
Ûabbar
Si©©iewi
St Julians
Fgura
Balzan
Qrendi
San Ìwann
Luqa
Lija
Safi
St Venera
Paola
Iklin
Ûejtun
Sliema
St Lucia
Mtarfa
Ûurrieq
Swieqi
Tarxien
Ta’ Xbiex
Xg˙ajra
at 5-6 years of age.1 The 2007 dataset was reanalysed in order
to obtain values for overweight and obesity, for both genders,
using the new WHO criteria.2
Localities
Children were allocated by current address to one of six
geographical sectors in a distribution devised by the Maltese
Office of National Statistics. Towns and villages included in the
relevant regions are shown in Table 1.
Schools
Education in Malta is based on the British model and
education is compulsory between the ages of 5 and 16 years.
Schooling in Malta is provided by: 1. State Schools, 2. Churchrun schools and 3. Independent schools. Education in State
schools is free of charge, Church-run schools accept voluntary
Table 2: Summary statistics for BMI by gender
2008
2010
Male
Female
Male
Female
17.0
16.9
18.6
18.4
0.1
0.1
0.1
0.1
16.3
16.2
17.6
17.3
Standard
deviation
2.9
2.8
3.8
3.7
Sample
variance
8.2
7.6
14.4
13.8
Kurtosis
7.8
4.5
2.9
2.2
Mean
Standard
error
Median
Skewness
n
Percentage
2.2
1.7
1.5
1.4
1754
1680
1558
1531
51.1
48.9
50.4
49.6
Malta Medical Journal Volume 23 Issue 01 2011
donations, whereas parents who opt to send their children to
Independent Schools are charged a fee. All of these schools were
involved in this study. The following two schools were excluded:
a) Verdala International School catering almost exclusively to
the children of expatriates, b) The Miriam al-Batool school which
caters almost exclusively for Muslim children who are short- or
long-term residents in Malta and one or both of whose parents
are not Maltese.
Definitions
The criteria used to identify overweight and obesity were
based on the 2007 World Health Organisation (WHO) child
growth reference charts of BMI-for-age for 5-19 years of age
for boys and girls respectively.2 As internationally accepted,
children whose BMI was over the 85th percentile for age were
considered overweight, while those whose BMI was above the
97th percentile for age were considered obese. A normal BMI
for adults is from 18.5 to 24.9 kg/m2, overweight is defined as
a BMI in the range of 25 to 29.9 kg/m2 and obese is defined as
a BMI over 30 kg/m2.
Results
General
In 2008, out of the 3734 students attending the second year
of primary school, 120 were born before 2001 and 179 students
were absent on the day of measurement. Therefore the surveyed
population was 3435 (mean age of 6.8 years). In 2010, out of
3723 students attending the fourth year of primary school,
160 were born before 2001 and 473 were absent on the day of
measurement. The surveyed population in 2010 was 3090 (mean
age of 8.8 years) resulting in a 10% decrease in participation
between the two years of assessment. Comparative summary
statistics for BMI by gender are shown in Table 2.
The main results defining overweight and obesity are shown
in table 3 (the first column of results dating to 2007 are derived
35
from an earlier study).1 There is a dip in mean BMI for both
overweight and obesity, for both genders, in the same cohort
of children over the span of 3 years, followed by a rise to levels
above the starting BMI of this study. The only exception is female
obesity which simply rises steadily over the course of this study.
The same cohort of children (those born in 2001) had also
been studied when they were 5-6 years old,1 and there is an
overall increase in overweight and obesity rates over the 3 years
that have elapsed between the first collection of data and the
last (Table 3).
By geographical area
The children’s home town or village was taken as reference.
In 2008, lower overall BMI’s were found in the Northern district
with the highest being found in Gozo (Table 4). In 2010, Gozo
maintained the highest overall BMI but the Northern Harbour
district had the lowest mean BMI.
If analysed by gender, then in 2008 the lowest BMI for boys
was in the Northern Harbour District and the highest in Gozo. In
2010 this changed to Northern District for the lowest BMI but
still was highest in Gozo. For girls in 2008, the lowest BMI was
in the Western District and the highest in the Southern Harbour
District. In 2010 the pattern remained the same except that the
highest BMI moved to South Eastern District. These differences
were significant for boys only.
By school
Table 5 displays the summary statistics for BMI by school
attended while table 6 details the distribution of overweight and
obese boys and girls by school. Figure 1 depicts quartile ranges
for the above. In 2008, boys attending independent schools
were the least overweight and obese while those attending Gozo
schools had the highest rate of overweight and obesity. Girls
attending independent schools in 2008 had the highest rate of
overweight and obesity and those attending Church schools had
the least. This situation showed a marked reversal in the case
of girls, with those attending independent schools being the
least overweight and obese. These differences were significant
for males only.
Discussion
The prevalence of obesity is rising at a very rapid rate
worldwide and it is projected that 150 million adults and 15
million children will be obese by the end of 2010.3 The trend in
obesity is especially alarming in children and adolescents. The
annual rate of increase in the prevalence of childhood obesity
has been growing steadily, and the current rate is 10 times that in
the 1970s. This will contribute to the obesity epidemic in adults
and creates a growing health challenge for the next generation.
This comparative study shows that Malta is no exception.
The Health Behaviour in School Children (HBSC) study is a
WHO 4-yearly initiative which assesses the health and lifestyle of
children aged 11, 13 and 15.4 The 2006 HBSC study reported that
Malta had the second highest proportion of obese or overweight
36
Table 3: Percentage overweight and obesity of the same
birth cohort (born 2001) by gender, over a 3 year period
(Criteria WHO 2007)
Year of assessment
2007
2008
2010
5.80
6.88
8.68
Total (n)
1792
1754
1558
Cutoff overweight (BMI)
Mean age (yrs)
Males
16.75
17.10
17.75
Overweight (n)
369
304
430
Overweight (%)
20.6
17.3
27.6
18.25
18.75
19.75
Cutoff obesity (BMI)
Obesity (n)
349
301
317
Obesity (%)
19.5
17.2
20.3
Overweight + obese (n)
718
605
747
Overweight + obese (%)
40.1
34.5
47.9
Total (n)
1669
1680
1531
Cutoff overweight (BMI)
Females
17.10
17.40
18.25
Overweight (n)
311
239
338
Overweight (%)
18.6
14.2
22.1
Cutoff obesity (BMI)
18.85
19.40
20.75
Obesity (n)
215
261
266
Obesity (%)
12.9
15.5
17.4
Overweight + obese (n)
526
500
604
Overweight + obese (%)
31.5
29.8
39.5
children amongst 11 and 13 year olds second only to the USA,
and the highest proportion of obese and overweight 15 year olds
when compared to the 41 countries participating in the study.
In all three age groups, between 28% and 31% of children had
a self-reported BMI that was greater than 25.
Childhood obesity is an important predictor of adult
obesity.5,6 Metabolic and cardiovascular risk profiles tend to
track from childhood into adult life, resulting in an elevated risk
of ill health and premature mortality.7
The differences in districts shown in this study are difficult
to interpret due to the relatively small numbers. The previous
significant incidence of overweight and obesity in boys living
in the Southern Harbour district, found in 2007, has now
petered out and all districts have shown more or less the same
increase in overweight and obesity rates over the last 2 years.1
One may speculate that the rise in overweight and obese boys
in Gozo, when compared to their Maltese counterparts, may
be due a combination of more fast-food outlets sprouting up
on the island and more academic pressure being enforced on
Primary School boys in Gozo in order to guarantee entrance to
Malta Medical Journal Volume 23 Issue 01 2011
Table 4: BMI Differences by gender and district
Mean
Standard Error
2008
2010
Boys Girls
Boys
Girls
N Dist
Gozo
W Dist
S Harbour
N Dist
Gozo
W Dist
SE Dist
16.81
17.43
16.74
17.11
18.22
19.11
18.32
18.32
0.16
0.24
0.16
0.18
0.22
0.35
0.23
0.25
16.32
16.85
16.05
16.25
17.29
18.04
17.17
17.28
Standard Deviation
2.52
2.78
2.65
2.95
3.36
4.07
3.63
3.89
n
264
132
272
270
227
137
258
Median
242
t
-2.24
-1.55
-2.27
0.0045
p
0.013
0.06
0.01
0.5
the past, has given way to ready-made convenience and other
energy-dense foods, as it has in Malta.
The school differences show that Independent Schools enjoy
the least prevalence of overweight and obesity among both
boys and girls. This was not so in 2008 when girls attending
Independent Schools had a high prevalence for overweight but
not obesity. However, this trend was significantly reversed in the
2010 study where the same girls became the least overweight and
the Junior Lyceum or to the only Church Secondary School on
the island, enforcing a more sedentary lifestyle on these children.
Furthermore, Gozitans have over the recent years, experienced
a change in social behaviour from the rural to the more urban
way of life with less time spent outdoors and more time in front
of televisions and computers, as has the rest of the country. It
might also be assumed that the more traditional and healthier
Mediterranean Diet which was typical for Gozo families in
Table 5: Summary statistics for BMI by school attended
2008
Males (n=1754)
Females (n=1680)
State
Church
Indep
Gozo
State
Church
Indep
Gozo
17.2
16.8
16.5
17.2
16.9
16.7
17.1
17.0
0.1
0.1
0.1
0.2
0.1
0.1
0.3
0.2
Median
16.3
16.4
16.2
16.7
16.3
16.1
16.3
16.4
Mode
16.3
14.4
13.1
15.4
13.9
16.6
15.8
12.8
3.2
2.4
2.0
2.7
2.9
2.6
3.1
2.5
10.0
5.9
4.1
7.4
8.2
6.6
9.7
6.2
Mean
Standard Error
Standard Deviation
Sample Variance
Kurtosis
7.1
6.6
3.1
5.4
5.0
3.9
3.2
1.9
Skewness
2.2
2.0
1.4
1.9
1.8
1.7
1.6
1.3
1018
368
248
120
832
598
141
109
n
F=5.2, p=0.001
2010
Males (n=1558)
F=1.1, p=0.4
Females (n=1531)
State
Church
Indep
Gozo
State
Church
Indep
Gozo
18.9
18.4
17.8
18.9
18.5
18.2
18.7
18.5
0.1
0.2
0.2
0.3
0.1
0.1
0.4
0.3
Median
17.7
17.7
17.2
18.0
17.3
17.3
17.4
17.3
Mode
16.4
17.0
20.7
15.4
14.0
13.8
15.1
20.1
4.1
3.4
2.9
3.7
3.8
3.5
4.2
3.7
16.7
11.6
8.5
14.0
14.7
12.0
17.4
14.0
Kurtosis
2.3
4.8
3.0
1.2
2.0
1.7
3.5
2.0
Skewness
1.4
1.7
1.4
1.3
1.3
1.2
1.9
1.4
894
342
198
124
716
578
115
122
Mean
Standard Error
Standard Deviation
Sample Variance
n
F=5.1, p=0.002
Malta Medical Journal Volume 23 Issue 01 2011
F=0.7, p=0.5
37
Table 6: Distribution of overweight and obese boys and girls by school
State
Church
Independent
Gozo
O/weight Obese Total O/weight Obese Total O/weight Obese Total O/weight Obese Total
2008 Males
Females
2010 Males
Females
13.7
19.8
33.5
16.3
14.9
31.2
16.1
10.5
26.6
21.6
17.5
39.1
16.7
14.1
30.8
15.4
12.2
27.6
27.7
12.8
40.5
15.6
13.8
29.4
17.4
27.8
45.2
23.4
22.8
46.2
15.1
19.1
34.2
21.8
27.4
49.2
14.3
22.7
37.0
19.2
18.7
37.9
9.7
9.3
19.0
15.6
20.5
36.1
Figure 1: Quartile plot of BMI by school for both genders and years studied (2008 and 2010).
BMI by school: Females 2008
24
22
22
20
20
18
18
10
BMI by school: Females 2008
30
28
28
26
26
24
24
22
22
18
12
12
10
10
State
14
Gozo
14
Independent
16
Church
16
Gozo
18
20
Independent
20
Church
BMI kg/m2
30
State
BMI kg/m2
State
Gozo
10
Independent
12
Church
12
BMI by school: Males 2010
38
14
Gozo
14
16
Independent
16
Church
BMI kg/m2
24
State
BMI kg/m2
BMI by school: Males 2008
Malta Medical Journal Volume 23 Issue 01 2011
obese when compared to other schools. A survey of school sports
facilities and time spent by children in physical activity per week
in the different schools, was carried out as part of the European
Child Growth Surveillance Initiative in 2008. This showed that
Independent Schools had longer school days, and more time
devoted to physical activity than State and Church Schools
(Sammut A, Public Health Specialist - personal communication).
This may be a contributing factor to the lower overweight and
obesity rates seen in children attending Independent Schools.
Another factor that should be taken into consideration is that
parents of children attending Independent Schools tend to have
a higher educational level and socio-economic status (WHO
European Childhood Obesity Surveillance Initiative (COSI) –
unpublished preliminary report – personal communication from
VFS) and hence a heightened awareness of the consequences of
overweight and obesity, and the ways in which to avoid these
conditions. However, several studies show that the risk of obesity
crosses all socio-economic and ethnic strata, despite being more
prevalent in low income groups.8,9
The health consequences of overweight and obesity in
children are not as clear as those for adults. Systematic review
shows that childhood obesity is strongly associated with
risk factors for cardiovascular disease and type 2 diabetes,
orthopaedic problems and mental disorders. Many obesity
related health conditions once thought to be applicable only to
adults are now being seen among children and with increasing
frequency. Examples of these include high blood pressure, early
symptoms of coronary artery plaque formation, type II diabetes,
non-alcoholic fatty liver disease, polycystic ovary disorder and
sleep apnoea. In addition to the physical health consequences,
severely obese children report a lower health-related quality of
life. Childhood obesity is a highly stigmatised condition often
associated with low self-esteem, and obese children are more
likely than non obese children to feel sad, lonely and nervous.10
Obesity imposes an economic burden on society through
increased direct medical costs incurred to treat the diseases
associated with it, and indirect costs due to lost productivity
because of absenteeism and premature death. In the European
Region, the direct health care costs of obesity account for 2-4%
of national health expenditure. The indirect costs could amount
to twice those for direct costs.11 A cautious figure for the Maltese
national health system has estimated that €20 million annually
is currently being spent from the health budget as a result of the
health consequences of overweight and obesity (Calleja N, Gauci
D – paper presented at the Malta Medical School Conference,
2010, personal communication). This figure will continue to rise
if the current trend in the prevalence of overweight and obesity
in our child population remains unrestrained and indeed, in the
2007 study, it was estimated that this figure would realistically
climb to €70 million within a few years.1
Obesity is a complex entity and cannot be viewed simply as
a health issue. Health education is effective in disseminating
Malta Medical Journal Volume 23 Issue 01 2011
knowledge and increasing motivation to change attitudes, but
is highly unlikely to achieve sustained behavioural change on
its own.
In its document The Challenge of Obesity in the WHO
European Region and the strategies for response published in
2007, the World Health Organisation advises that measures to
combat obesity need to be undertaken by a range of entities such
as agriculture, transport, commerce and industry, education,
the mass media and communication. Without this cross-sector
collaboration success in controlling and indeed, reversing the
obesity epidemic cannot be achieved. No single action will
reverse this epidemic but there is no doubt that improving
eating habits and increasing voluntary and involuntary daily
physical activity are two critical strategies. Tackling the causal
factors of obesity at an early stage requires a multi-sectoral and
multifactor approach.
Furthermore , a strong evidence base of data must continue
to be built in order to track the success of interventions. Hence,
continuous monitoring of key indicators such as children’s
height and weight is essential. This study has followed up one
national cohort of Maltese children over three years. The same
cohort will be followed up again in 2012. Whilst additional
studies to identify the precise causes of obesity will be useful,
specific actions can and should be integrated in order to prevent
or at least limit, and address obesity within Maltese society.
The development of this integrated approach would help to
track the effectiveness of interventional or prevention strategies
and provide an anchor by which policy makers can implement
suggested actions.
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